A superconducting wire is manufactured by superposing a metal substrate and one or more intermediate layers composed of oxides, such as cerium oxide (CeO2), yttria-stabilized zirconia (YSZ), and yttrium oxide (Y2O3), and a buffer layer on top of each other, so as to form a laminated substrate for a superconducting wire (i.e., a laminated substrate for epitaxial growth), and further superposing a superconducting layer (RE123 film, RE: Y, Gd, Ho, Sm, Dy, or the like) thereon.
It is known that, as the degree of crystal orientation of a superconducting layer is improved, the resulting superconducting wire exhibits improved superconducting properties. A superconducting layer is manufactured via, for example, vapor-phase growth techniques, such as sputtering or pulsed laser deposition (PLD), or liquid-phase growth techniques, such as metal organic deposition (MOD), by preparing a laminated substrate for a superconducting wire with a crystal-oriented surface layer and allowing the crystals of an oxide superconducting material to grow in a given direction on the laminated substrate. In order to improve the degree of crystal orientation of a superconducting layer, accordingly, it is effective to improve the crystal orientation of the laminated substrate for a superconducting wire.
As a technique for manufacturing a laminated substrate for a superconducting wire with excellent crystal orientation (i.e., a laminated substrate for epitaxial growth), for example, Patent Document 1 discloses a method of manufacturing a substrate comprising: a process for preparing a base material wherein a nickel layer is formed on a copper layer by a plating method; a process for heat-treating the nickel layer at 800° C. to 1,000° C.; and a process for epitaxially growing an intermediate layer, such as a CeO2 thin film, on the nickel layer after the process for heat-treating the nickel layer. The biaxial orientation of the intermediate layer is improved by such method. In addition, Patent Document 2 discloses a method for producing an oxide superconducting thin-film wire comprising an oriented metal substrate, an intermediate layer laminated thereon, and an oxide superconducting layer laminated thereon, wherein the process for forming the intermediate layer at least comprises a process for forming a CeO2 layer on the oriented metal substrate via RF sputtering and a process for forming a Y2O3 layer on the CeO2 layer via electron beam evaporation.